1. Field
Example embodiments relate to a light emitting device (LED) manufactured by using a wafer bonding method, and to a method of manufacturing a LED using a wafer bonding method.
2. Description of the Related Art
Light emitting diodes (LEDs) including a semiconductor material, e.g., a Group III nitride semiconductor, or a Zn—Mg—O-based semiconductor material, may be made relatively small and light and have a relatively long lifetime. Various technologies have been developed to increase the efficiency of LEDs. Recently, in order to use a LED as a conventional lighting device, research on high-output and high-brightness LEDs has been conducted. However, because of the structure of a LED, when high-power is supplied to a LED, the efficiency of the LED decreases as compared to a case where low-power is supplied to a LED.
Thus, a vertical type LED having an efficient current application structure has been proposed. Unlike a horizontal type LED in which a part of a semiconductor layer is etched and an electrode is formed in the etched part, the vertical type LED may be directly located in an upper surface and a lower surface of the semiconductor layer. Accordingly, the vertical type LED has improved efficiency and higher output as compared to the horizontal LED. The vertical type LED is also more easily cooled as compared to the horizontal type LED, because heat generated during operation thereof is more easily radiated to the outside.
On the other hand, in the case of the vertical type LED, because an electrode should be located in upper and lower surfaces of a semiconductor layer, the vertical type LED requires a different manufacturing process from the horizontal type LED. For example, after a semiconductor layer is grown on a growth substrate, e.g., sapphire, the growth substrate is removed in order to perform subsequent processes. Before removing the growth substrate, plating (via a plating method) or wafer bonding (via a wafer bonding method) is performed with respect to the semiconductor layer so as to stably fix the semiconductor layer from which the growth substrate is to be removed.
When plating is used, difficulties may arise in performing the entire process due to a decrease in flatness and solidity of the plated metal thin film. When wafer bonding is used, a crack may occur in the semiconductor layer during a cooling process performed after wafer bonding, due to a difference of expansion coefficients of the growth substrate, e.g., sapphire, and a new bonding substrate. Also, the entire structure of the semiconductor layer may bend or warp.